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Subject[PATCH 5.5 094/367] mmc: spi: Toggle SPI polarity, do not hardcode it
From: Linus Walleij <>

commit af3ed119329cf9690598c5a562d95dfd128e91d6 upstream.

The code in mmc_spi_initsequence() tries to send a burst with
high chipselect and for this reason hardcodes the device into

This is not good because the SPI_CS_HIGH flag indicates
logical "asserted" CS not always the physical level. In
some cases the signal is inverted in the GPIO library and
in that case SPI_CS_HIGH is already set, and enforcing
SPI_CS_HIGH again will actually drive it low.

Instead of hard-coding this, toggle the polarity so if the
default is LOW it goes high to assert chipselect but if it
is already high then toggle it low instead.

Cc: Phil Elwell <>
Reported-by: Mark Brown <>
Signed-off-by: Linus Walleij <>
Reviewed-by: Mark Brown <>
Signed-off-by: Ulf Hansson <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/mmc/host/mmc_spi.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

--- a/drivers/mmc/host/mmc_spi.c
+++ b/drivers/mmc/host/mmc_spi.c
@@ -1134,17 +1134,22 @@ static void mmc_spi_initsequence(struct
* SPI protocol. Another is that when chipselect is released while
* the card returns BUSY status, the clock must issue several cycles
* with chipselect high before the card will stop driving its output.
+ *
+ * SPI_CS_HIGH means "asserted" here. In some cases like when using
+ * GPIOs for chip select, SPI_CS_HIGH is set but this will be logically
+ * inverted by gpiolib, so if we want to ascertain to drive it high
+ * we should toggle the default with an XOR as we do here.
- host->spi->mode |= SPI_CS_HIGH;
+ host->spi->mode ^= SPI_CS_HIGH;
if (spi_setup(host->spi) != 0) {
/* Just warn; most cards work without it. */
"can't change chip-select polarity\n");
- host->spi->mode &= ~SPI_CS_HIGH;
+ host->spi->mode ^= SPI_CS_HIGH;
} else {
mmc_spi_readbytes(host, 18);

- host->spi->mode &= ~SPI_CS_HIGH;
+ host->spi->mode ^= SPI_CS_HIGH;
if (spi_setup(host->spi) != 0) {
/* Wot, we can't get the same setup we had before? */

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